Odontogenic Tumours Classification

Classification of Odontogenic Tumours

• Based on cell of origin:
  • Tumours of Odontogenic Epithelium (dental lamina + enamel organ)
  • Mixed Tumours (odontogenic epithelium + ectomesenchymal tissue with or without dental hard tissues)
  • Tumours of Ectomesenchymal Tissue (cells of the dental papilla)

Odontogenic Tumours - General Rules

• Very uncommon
• Generally benign, although some may exhibit aggressive behaviours
• Malignant odontogenic tumours are extremely rare

Clinical Presentation

• Ranges from incidental finding to an asymptomatic expansile mass
• Can present as unilocular or multilocular lesions
• May or may not be associated with a tooth

Odontogenic Epithelium Tumours (benign)

• Ameloblastoma
  • Conventional, Unicystic, Extra-osseous/Peripheral, or Metastasizing
• Adenomatoid Odontogenic Tumour (AOT)
• Calcifying epithelial odontogenic tumour (rare)
• Squamous odontogenic tumour (rare)

Ameloblastoma

• Benign tumour of odontogenic epithelium
• Huge growth potential and infiltrative growth pattern
• High recurrence rate if simply curetted
• Can extend into base of the brain and cause death if left untreated

Clinicopathologic Types of Ameloblastoma

• Conventional
• Unicystic
• Peripheral
• Metastasizing (very rare)

Epidemiology of Ameloblastoma

• Rare under the age of 10
• Uncommon in 10-19 years old
• Equal prevalence in 3rd to 7th decade
• 80-85% occur in the mandible (usually posterior)

Clinical Presentation of Ameloblastoma

• Painless swelling or expansion
• Capable of significant growth if left untreated
• Pain and paresthesia are uncommon

Radiographic Presentation of Ameloblastoma

• Multilocular radiolucency (soap bubble or honeycomb appearance)
• Expansile lesion with thinning of the cortices
• Found in any relation to the teeth or with no adjacent tooth
• Radiographic margins range from well- to ill-defined, but usually somewhat defined
• Root resorption is common

Histopathology of Ameloblastoma

• Hyperchromatic nuclei of ameloblast-like basal epithelium
• Stellate reticulum-like cells
• Some discrete keratin formation in the middle
• An ameloblastoma island is like an inverted dental organ, with the ameloblastoma-like cells on the periphery

Unicystic Ameloblastoma

• Cystic tumour lined by odontogenic epithelium with a low recurrence rate
• Tend to present in the second decade most commonly
• 90% in mandible – predilection for the posterior
• Clinical and Radiographic Presentation: Unilocular, pericoronal radiolucency

Variants of Unicystic Ameloblastoma

• Intraluminal
  • Papillary appearance to the lumen of the tumour (gross appearance)
  • Plexiform growth pattern in the odontogenic epithelium
• Luminal
  • Mural

Management and Prognosis of Ameloblastomas

• Conventional (conventional and mural)
  • 5-17% recurrence rate with resection
  • 30-35% with curettage or enucleation
• Unicystic (luminal and intraluminal)
  • 6-37% recurrence
• Peripheral ameloblastoma
  • No recurrence with simple excision

Adenomatoid Odontogenic Tumour (AOT)

• Definition: Uncommon benign tumour of odontogenic epithelium
• Epidemiology: Teenagers – rarely over age 30, strong female predilection (2:1), loves the maxilla (2:1)
• Clinical Presentation:
  • 2/3 adolescents
  • 2/3 females
  • 2/3 maxilla
  • 2/3 associated with unerupted root
• Radiographic: Initially radiolucent, then flocculent opacities (“snowflakes”)
• Treatment: Encapsulated – thus enucleates cleanly on curettage, when a tooth is involved, the tooth is extracted, rarely recurs

Calcifying Epithelial Odontogenic Tumour (CEOT)

• Definition: Benign, aggressive neoplasm of stellate intermedium and/or reticulum
• Less aggressive than ameloblastoma
• Epidemiology and Clinical Presentation: Rare, most common presenting sign is a painless, slow-growing swelling
• Radiographic Presentation: Unilocular (more in maxilla) or multi-locular, margins are typically scalloped and well-defined; may be corticated or ill-defined
• Histopathology: Clusters of polyhedral epithelial cells, often intercellular bridges, large and dysplastic-looking cells, background fibrous stroma

Learn about the classification of odontogenic tumours based on the cell of origin, including tumours of odontogenic epithelium, mixed tumours, and tumours of ectomesenchymal tissue. Understand the general rules and characteristics of odontogenic tumours.